Sub-Nanometer Catalyst Clusters for Propane Dehydrogenation

Propane dehydrogenation (PDH) is used to produce propene, which is the primary building block for many commercial plastics. The catalyst most commonly used for this reaction is platinum. Due to rising demand for propene, an alternative catalyst is being sought due to platinum’s high cost. Alternatives might involve very small platinum particles as well as particles composed of different atoms. For this purpose, we have performed a computational study of the PDH reaction with a 4 atom platinum cluster (Pt4) and several different 4-atom transition metal cluster (TM4) catalysts on a graphene support. We have computed the equilibrium structures of the Pt4 and TM4 clusters on both single-and double-vacancy sites and have calculated the complete PDH reaction pathway for each case. This allowed us to study the effect of the graphene support on catalytic activity. We have also calculated the PDH reaction pathway for larger Ptx clusters, where x = 5-14, in order to study the effect of particle size on catalytic activity. These results help clarify the relationship between the PDH activation energy and the propane binding energy and overall reaction energy and may aid in the design of new potential catalysts for the PDH reaction

Raising fertility: Lessons for Germany from cross-country comparisions?

This paper aims at identifying the conditions which drive successful family policy. Therefore, it is necessary to know the economic and sociodemographic situation of families which is investigated in eight OECD countries. Special attention is drawn to income, education and labor supply of the parents as well as to the redistributive impact of family payments. Significant differences can be identified and conclusions for an effective family policy are presented

Face-to-face and online interactions - is a task a task?

This study contrasts two different ways of analysing interaction and participation in language learning tutorials: Social network analysis of frequency and QSR analysis of type of interaction. One task from three German beginners' language tutorials (one delivered face-to-face, the other two online) is analysed. A description of the background and method of the study is provided together with some examples of the findings. As this is work in progress, only tentative conclusions can be provided at this stage

Learning to share and sharing to learn – professionaldevelopment of language teachers in HE to foster open educational practices

This case study presents the staff-development perspective of the ‘Collaborative Writing and Peer Review Project’ developed at the Department of Languages, at the Open University, UK, between November 2011 and March 2012. The project was set up to promote the professional development of teachers through collaborative writing and peer review, encouraging open educational practices (OEP) and by extension the production and publication of teaching resources in an open repository. As teacher developers working in a blended environment, the authors facilitate opportunities for sharing and developing good practice as part of a broad staff development programme to help teachers understand and integrate innovative approaches into their practice. Participants in this project brought with them a range of experiences as practitioners from their work with language students both at and outside the University. This case study focuses on the professional development aspect of this initiative. It presents the different aspects of the process and analyses teachers’ involvement with social online tools and the impact on teaching practice of engaging with the process of collaboration

Distance and virtual distance: Preliminary results of a study of interaction patterns in synchronous audio graphic CMC and face-to-face tutorials in beginners’ language tutorials

This paper presents preliminary results of a larger study of interaction patterns in beginners’ language tutorials held at the Open University. The tutorials are voluntary, supplementing a distance learning course in German as a Foreign Language. Tutorials are offered in two versions: traditional face-to-face tutorials in a classroom or online tutorials held through an internet based audio-graphic conferencing system. Interaction patterns are compared between the two modes of presentation, between different tasks performed by students and between different tutors initiating the same task. Results of the completed study will be published in 2005 / 06

Computational Analysis of the External Aerodynamics of the Unpowered X-57 Mod-III Aircraft

Investigations of the external aerodynamics of the unpowered X-57 Mod-III configuration using computational fluid dynamics are presented. Two different Reynolds-averaged Navier-Stokes flow solvers were used in the analysis: the STAR-CCM+ unstructured solver using polyhedral grid topology, and the Launch Ascent Vehicle Aerodynamics (LAVA) structured curvilinear flow solver using structured overset grid topology. A grid refinement study was conducted and suitable grid resolution was determined by examining the forces and moments of the aircraft. Code-to-code comparison shows that STAR-CCM+ and LAVA are in good agreement both in quantitative values and trends. The angle-of-attack sweep and sideslip-angle sweep were performed. Results indicate that lift coefficients have a sharp drop at stall. At high angle of attack, STAR-CCM+ and LAVA show different flow separation behavior possibly due to differences in the turbulence model. The sideslip-angle sweep results show constant pitching moment from 0 to 15, then a sharp increase between 15 and 20 sideslip angle

Study of Laminar-Turbulent Transition Modeled by Amplification Factor Transport Within the LAVA Solver

The Amplification Factor Transport (AFT) transition model proposed by Coder and Maughmer is implemented in the unstructured and curvilinear Reynolds-Averaged Navier-Stokes (RANS) solvers of the Launch Ascent and Vehicle Aerodynamics (LAVA) platform. It is coupled to the Spalart-Allmaras (SA) turbulence model through a modified intermittency variable. As part of the model verification and validation phase, laminar-turbulent transition is studied over 2D flat plates, wind turbine and general aviation airfoils, as well as a 3D inclined prolate spheroid and the JAXA Standard Model (JSM). This work will analyze the sensitivity of the results to grid refinement, grid paradigm, flow conditions and numerical schemes. The numerical efficiency of the unstructured and curvilinear solvers will be compared and convergence acceleration techniques will be explored to address a broad range of aerodynamics applications

Computational Simulations of a Mach 0.745 Transonic Truss-Braced Wing Design

A joint effort between the NASA Ames and Langley Research Centers was undertaken to analyze the Mach 0.745 variant of the Boeing Transonic Truss-Braced Wing (TTBW) Design. Two different flow solvers, LAVA and USM3D, were used to predict the TTBW flight performance. Sensitivity studies related to mesh resolution and numerical schemes were conducted to define best practices for this type of geometry and flow regime. Validation efforts compared the numerical simulation results of various modeling methods against experimental data taken from the NASA Ames 11-foot Unitary Wind Tunnel experimental data. The fidelity of the computational representation of the wind tunnel experiment, such as utilizing a porous wall boundary condition to model the ventilated test section, was varied to examine how different tunnel effects influence CFD predictions. LAVA and USM3D results both show an approximate 0.5 angle of attack shift from experimental lift curve data. This drove an investigation that revealed that the trailing edge of the experimental model was rounded in comparison to the CAD model, due to manufacturing tolerances, which had not been accounted for in the initial simulations of the experiment. Simulating the TTBW with an approximation of this rounded trailing-edge reduces error by approximately 60%. An accurate representation of the tested TTBW geometry, ideally including any wing twists and deflections experienced during the test under various loading conditions, will be necessary for proper validation of the CFD

Establishing Best Practices for X-57 Maxwell CFD Database Generation

The X-57 Maxwell is NASAs latest electric airplane concept that has been simulated for aerodynamic performance using the structured overset and unstructured grid solvers within the Launch Ascent and Vehicle Aerodynamics (LAVA) solver framework as well as the unstructured polyhedral grid solver in Star-CCM+ for code-to-code comparison. In order to validate the predictions, comparisons were made between the CFD solutions and experimental data collected in the 12-foot Low-Speed Wind Tunnel at NASA Langley Research Center. The simulations are in preparation for the development of a comprehensive aerodynamic database which will assess aircraft performance at a variety of conditions. The findings from these simulations will establish the best practices for mesh resolution, numerical discretization, and turbulence modeling to be used for this database. Preliminary database results have shown that best-practices learned from the initial validation simulations will potentially reduce error in X-57 aerodynamic loads and moments relative to experiment by up to 14%

Identification of genes encoding squalestatin S1 biosynthesis and in vitro production of new squalestatin analogues

A gene cluster responsible for the biosynthesis of squalestatin S1 (SQS1, 1) was identified by full genome sequencing of two SQS1-producing ascomycetes: Phoma sp. C2932 and unidentified fungus MF5453. A transformation protocol was established and a subsequent knockout of one PKS gene from the cluster led to loss of SQS1 production and enhanced concentration of an SQS1 precursor. An acyltransferase gene from the cluster was expressed in E. coli and the expressed protein MfM4 shown to be responsible for loading acyl groups from CoA onto the squalestatin core as the final step of biosynthesis. MfM4 appears to have a broad substrate selectivity for its acyl CoA substrate, allowing the in vitro synthesis of novel squalestatins